No.49 April, May 1983 EXPLOITATION OF CLAM SHELL DEPOSITS IN THE ESTUARY*

The Kundapur estuary is the largest estuarine sys­ Each boat is tied to 2 to 3 casuarina poles fixed in tem in the Dakshina district of the river bed. The second (rear) boat is positioned with a water spread of about 26 sq. km, situated about parallel in line with the first boat in such a way as to 100 km north of , and is important for clam leave a gap of 1 m in between, also lying 1 m to the left landings. Till recently the sub-soil shell deposits in the of the first boat. The dredge is driven well into the bed estuary were exploited on a very limited scale due to from the first boat and the rope is pulled up over the poor demand. The establishment of a polyfibre indu­ pulley in the rear boat. A person in the first boat takes stry in«Harihara has opened up a new avenue for lime charge of the cleaning rope. The dredge is pulled to shell utilisation and, consequently, lime shell produc­ collect the shells which are cleaned by lifting the cod tion has attracted the attention of poor people. The end of the net. Then the shells are emptied into the introduction of a simple but effective device for collec­ first boat. Each operation normally takes 2-3 minutes. tion of clam shells in 1975 proved to be a turning point In a single operation about 10 to 20 kg of shells are in the exploitation of the resource. The shell deposits hauled up depending upon the thickness of the shell are comprised of Meretrix casta - 40%, Meretrix mere- layer. The boats used for collection of shells are usually trix -25%, Paphia malabahca -25% and others (Ana- of 1 tonne capacity. Each site may yield shells for one dara Cerethedia and oysters) - 10%. or two weeks before it gets exhausted. The site again becomes productive after a couple of months or more, Description of shell dredge with the filling of shells due to movement of the loos­ The dredge used for the collection of shell depo­ ened layer of shells around it. sits is locally called "machine" (Fig.l). It consists of a semicircular iron ring, to the free ends of which is fitted Shell Production a slightly curved iron base plate of about 42 cm length, A unit of a pair of boats collects about two tonnes having 19-20 spikes pointing downwards. The height of of shells a day. There are about 85 units operating in the plate with spikes is 4.5 cm. To the middle of this Kundapur estuary. During the south-west monsoon spiked plate, an iron piece (about 13 cm length) is season the number of units may be as high as 125, as rivetted to which a wooden piece of about 60-65 cm is the fishermen gets a gainful occupation during the off attached. A bamboo pole, 6.5 m long, is tied to the season. The total production of shells varies from 150 wooden piece. An iron chain of about 3 m length is to 175 tonnes per day. Boats of 10 tonnes capacity are rivetted to the free ends of the ring. To the middle of used for transporting shells from the collection sites to this chain a nylon rope of about 10-11 m is tied. The the selling point. Mechanised shell washers with run­ arrangement facilitates dragging of the dredge over a ning water are used for further cleaning shells. In this pulley attached to the boat. A net is attached to the process small broken pieces of shells, sand and mud device to hold the shells being dredged. To the cod constituting about 10-15% are removed. A co-oper­ end of the net a 2m rope is tied on the inside, which ative organisation "Swawalambi Sangh" of Kundapur, could be pulled up and down for cleaning the shells. purchases all the lime shells directly, eliminating the middlemen, and thus protects the economic interests Operation of dredge of shell collectors. The shells are sold by the Sangh at A pair of b9ats is employed for the operation of Rs 85-100/tonne at Kundapur. the dredge. Each boat is manned by two persons. Usu­ ally they go out for collection early in the morning and The estimated production of lime shells in Kunda­ return by mid-day. Initially the estuarine bed is sound­ pur estuary during 1975 to 1982 (July-June) is given ed to detect the shell deposits. The shell collectors below: thrust a bamboo pole into the bed till the shell layer is Year Production (tonnes) reached and drive it deeper to know the thickness of 1975-76 13,500 the bed which is measured by the sound made by the 1976-77 21,540 thrust of the pole through the shells. The prospecting 1977-78 22,000 is usually not carried out daily as one site may yield shells for a few days. "Prepared by G. Syda Rao

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•bamboo pole (6-5 m )

wooden piece -iron ring

iron plate spiked plate ron chain rope for cleaning

Fig.l. Construction details of shell dredge.

1978-79 19,680 used for treatment of effluents, to neutralise soils of cof­ 1979-80 22,470 fee and tea plantations, and as a pesticide by mixing 1980-81 2f9,540 with copper sulphate. The finer bits of shells are mixed 1981-82 14,325 in the poultry feed. 1982-83 6,000 Present status of shell collection (Upto Dec. '82) About 450 people are employed practically throug­ hout the year. At present the shell collection is con­ As stated earlier the major user of these shells is centrated around. 'Uppena Kuduru' is let in the the Harihara polyfibres. The shells form an important estuary. This estuarine area is about 138 ha and was. component of 'Chemical recovery process' in most of the leased out for 20 years, by the Department of Mines pulp (paper and rayon) industries. The shell lime is also and Geology, Government of Karnataka to the first five

21 Fig.l General view of Kundapur estuary, showing a Rg.2. Dredge, locally called "machine", hauled with shells. number of units engaged in shell collection

Fig!3. Close-up view of the pulley attached to the rear boat to Fig.4. A view of heaps of cleaned shells near a lime factory at pull up the dredge. Kundapur. years and Rs.36, during the rest of the 15 years. Furt­ the substraiusm and prevented the settlement of her, they have to pay Rs.4/tonne of exploited shells as clams. Extensive operation of dredge has adversely 'royalty'. In addition to Kundapur estuary, about 247 ha affected one of the clam beds in the sea between Can- in the estuary and 293 ha in the goli and Uppena Kuduru. Regulatory measures are estuary have already been leased out for the exploita­ necessary for proper management of clam resource in tion of shell deposits. The deposits are noticed 1 to 1.5 these estuaries keeping the long-term benefits in view. m below the soil and the height of water column over The author is thankful to Dr.E.G. Silas, Director, ^he bed varies from 1.5 to 3 m. C.M.F.R.I for encouragement and to Dr. K. Alagars- General remarks wami, Head, MFD, for suggesting the study, guidance Very rarely a few live clams are found in the and critically going through the manuscript. Also dredge collections at present, indicating absence of thanks are due to Shri K.Devadas Pai, Swawalambi clam beds. But this area was known to yield good Sangh, Kundapur and Department of Mines and quantities of live clams, particularly Paphia malabarica, Geology, Mangalore, for their help. till 1978-79. Continuous dredging might have disturbed

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